Molding composition containing a reactive phenol-aldehyde condensation product and method of making the same



Patented Aug. 7, 1951 REACTIVE PHENOL-ALDEHYDE CONDEN- :SATION PRODUCTAND METHOD OF MAK- ING THE SAME Paul 0. Powers, Manheim Township,Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster,Pa., a corporation of Pennsylvania No Drawing.

Application September 29, 1944, Serial No. 556,475 V i Claims. (Cl.260-172) This invention relates to molding compositions. It is concernedparticularly with the problem of improving the water resistance of themolded product. The problem has been attacked from the standpoint of theutilization of base materials, particularly binder ingredients, whichwill impart the desired resistance to the product as molded, rather thanfrom the point of improving water resistance by treatment of the productsubsequent to molding.

Phenol formaldehyde resins in a partially condensed condition arecommonly used in the manufacture of molding powders. The dry resin inpowdered form is mixed with the base materials which generally consistlargely of a fibrous filler, such as wood flour, cotton flock, or thelike and color pigment. The formed products, while extensively usedcommercially,- are not sumciently water resistant for some purposes.This is believed to be due to the fact that the binder does not enterinto the inner fibrous structure of the filler, but merely lies on thesurface. This has required the use of fillers which are not moistureabsorbent, such as the mineral fillers. This is objectionable wherelight weight is desired and can be accomplished only with a sacrifice instrength of the finished product. It also has resulted in some instancesin an impairment of the surface finish of the product.

An object of the invention is to provide a molding powder which willproduce a finished article Another object of the invention is to providea cheap method of forming molding powders, by which the binder insolution is deposited within fibrous structure and the solvent removedbyroll milling.

According to this invention a binder is formed having a sufficientlysmall molecular size to favor adsorption and absorption. It is highlyreactive to insure a speedy cure under molding conditions. A producthaving these physical characteristics is one consisting essentially of areactive partial condensation product composed largely of o-hydroxybenzyl alcohol and omethylol-p-methylol phenol having a molecular weightbelow 300. This product is soluble in water in all proportions and isdistributed as a water solution over the fibrous filler. Rapidpenetration of the binder into the filler and impregnation of the innerfiber structure results. Subsequent to distribution of the bindersolution, the water may be driven off and the product dried by rollmilling the composition. Since the product is in a low stage ofpolymerization (possessing a molecular weight below 300), the heatdeveloped in milling to remove water is not objectionable even though itmay result in further polymerization and concomitant increase inmolecular weight. This is not possible with the phenolic resinscustomarily used in molding powders. They are not Water soluble, have amolecular weight above 700, and are not capable of displacing themoisture between the cells in thewood flour or other fibrous absorbentfiller.

As an example, the following resin may be prepared:

' Example I I 94 grams of phenol 112.5 cc. of 37% formalin 5 gramssodium hydroxide The mol ratio of formaldehyde'to phenol is equal to 1.5to 1. The ingredients are placed in. a reaction vessel, mixedthoroughly, and permitted to stand at room temperature, approximately 25C., for approximately 72 hours. The hydrogen ion, concentration of themixture is more alkaline than pH 10 and is preferably between pH 10.5and pH 12 during the entire reaction period. At the end of the reactionperiod, sufficient glacial acetic acid is added to halt the reaction andreduce the solution to pH 7-8. That quantity which is sufficient toneutrallze of the sodium hydroxide is generally satisfactory.

The product produced in accordance with the foregoing procedurepossesses a solids content of about 50% and is completely miscible inwater. The average molecular weight is well below 300. For bestresults,- the average molecular weight should fall in the range betweenabout and about 300. The product is composed largely of o-hydroxy benzylalcohol and omethylol-p-methylol phenol. The product is stable for longperiods of time and because of its low molecular weight, it possessesexcellent penetration powers. It is capable of displacing the water heldbetween the cell wallsof the wood flour commonly employed in preparingmolding compositions.

The following is another example of a product suitable for use in mymolding composition:

Example II 94 grams of phenol 188 cc. of 37% formalin 3 grams of sodiumhydroxide The mol ratio of formaldehyde to phenol equals 2.5 to 1. Theprocedure set forth in Example I is followed gin'making" the. product.In this example, as-in-Examp1e"-I;" the temperature of reaction shouldbe maintained below 40 C. and may be carried out at normal roomtemperature,- in the order of 25 C. This low temperature polymerizationat a pH between- 10.5 and 12 favors the formation of saligeninand'phenol dialcohol'. If the temperature of reaction is about 40 0.,about 24 hours time is required to obtain the desired product.

The product produced in Example IL possesses f a solids content of 40%.It is completely soluble in water and is stable for long periods oftime. It is composed largely of o-hydroxy benzyl alcohol andomethylol-p-methy1ol phenol, has an average molecular weight below 300,and is capable of rapid penetration into wood flour and similarabsorbent fibrous: fillers.

With this product, it is possible to use considerablylessbinder thancustomarywithout detracting from the desiredqualities in the finishedproduct. With the usual-phenolic resins, theminimum resinconcentrationis about 40% ofthe composition. In the preparation oftypical molding powder of my invention, 30-35% of the binder isdistributed: over 65-70% of wood flour. The binder is dissolved in-waterand as a specific example, 70 pounds of binder solution formed inaccordance with Example I, having a solids content of 50%, aredistributed over 65 pounds of wood flour ofthe usual molding powdergrade. The preferred practice is to incorporate the resin and wood flourin aamixing machine and after uniform distribution is obtained, tocharge portioni'ng of the binder and filler will vary over a relativelyWide range depending upon the type offiller used and its'mesh size, thetype of product tobe produced the finish desired, and

other variable factors. Theis'ame is true ofthe size towhich thematerial is finally ground or powdered. The milling time will dependupon the size ofthe-mill, the quantity milled per batch-,-

the solids content of the-binder, the proportioning ofbinderandfiller,and other elements which vary. v 1

The milling step advances the polymerization of the resin due to theheat developed and by proper control, the proper degree of cure foroptimum results inmolding may be attained.

Another practice which may be followed informing a moldingpowder istobake the mixture afteruniform distribution of the binder over thewoodflour by heating: the mixture to 80: to 90 C. in an oven for abouthours to-reduce the mois ture content to about 1%. The mass is thenbroken, ground, or powdered, and sieved to produce a moldingcomposition. A combination of milling and oven drying steps may befollowed. For best results, thecompositionshould be reduced to asubstantially bone dry condition whether accomplished on the mill or byoven drying or both.

Obviously, the temperature of alloperations up to actual molding must bemaintained below that at which the binder is completely cured, althoughsome polymerization mayad-vantageously take place on the mill rollsaaspreviously pointed out. Once the binder has beenabsorbedandiadsorbed'heldby similar forces.

by the wood flour, an increase in the molecular weight of the binderresin is not detrimental but may be desirable. The l'owgmoleculargweight is necessary only toperniit proper diffusion of the binder withinthe structure of the filler.

. It is believed that true water resistance is obtained when the binderis adsorbed by the filler, such adsorption taking place when adsorbedwater naturally occurring between the cell walls by forces approachingchemical bonds in strength is displaced by resin molecules which arethen This resin, after cure, becomes insoluble and renders the cellwalls and interstices between the cells impervious to water. Such actioncannot occur with the phenolic resins, customarily employed in moldingpowders and explains their lack of moisture resistance been renderedresistant, for only capillary action has been retarded by absorption ofthe resin onto the fibers. With the molding powders of the presentinvention both-absorption,- which restricts capillary action,and=adsorption,-which-limits diffusion, are obtained thu's producingafinal product which is unusually resistant to moisture.

In place of phenol in the binder product, meta cresol may be used or amixtureofmeta and para cresol, provided the meta cresol constitutes atleast 70% of the mixture; 3,5-Xylenolmay be used or 3,4 xylenol maybe'substituted. In all instances, thepI-I-must be more alkaline than pH10 and the temperature must be'below 40 C. in order toproduceareactive'partial condensation product which: is composed largelyof "o-h-ydroxy benzol alcoholand o-inethylol p-methylol-phenol. In placeof the 37% formalin referredto in Examples I and II, paraformaldehyde-may be used. In place of wood flouig otherabsorbentfibrous; fillers may-beemployed, such as cotton flock or linters', alphacellulose-flock, or' the like."

While I have described certain preferred embodiments of myfinvention itwill be understood that the'same may be otherwise-embodied and:practiced withinthesco'pe of the following claims.

Icla im I .13.. r

1. A method of making moldingcomposition comprising the stepsofimpregnating an absorbent fibrous filler with an impregnant consistingessentially of a reactive partial condensation productcomposed" largelyofo-hyd-roxy benzyl alcohol and o-methylol-p-methylol phenol hav meanaverage molecular weight below 300 dissolved in water, and removinga-substantial portion of the water fromsaid impregnated filler byrollmilling, i

2'. A method of making a molding-'- composi tion comprising the steps ofdistributing a an inrpregnant consistingess'entia'lly of a water s'olu-*tion of a reactive partial condensation, product composed largely of o"-hydroxybenzyl alcohol and omethylol-p'-methylol phenol over an ab'-=*sor-beri't fibrous filler, and milling saidj compo's'i-' tion to effectadsorption of'sai'd impregnant into the fibrous structure of thefillerand develop" heat in the composition to dry out 'a substantial quantityof the water and advanceithe resin to a degree of curesuitableformolding. H

\ 3. A method of makinga molding composition comprising the stepsyof.distributing an impregi nant consisting essentiallyof'. a-water solutionof a reactive. partial on ensation; pro -v posedlargely.ofo hydroxybenzylalpohol and omethylohp-methyl l vphenol; -.oy.e,1:. Wood. flour.mil-lingi said composition", to. v effect.adsorption of said impregnantinto the fibrous structure of the wood flour, and continuing millinguntil said composition is reduced to a substantially bonedry conditionand the resin advanced to a degree of cure suitable for molding.

4. A method of making a molding composition comprising the step ofmilling and partial heat curing a composition containing a wood flourfiller having absorbed and adsorbed thereon and therein a reactivepartial condensation product composed largely of o-hydroxy benzylalcohol and o-methylol-p-methylol phenol dissolved in water.

5. A method of making molding composition comprising the steps ofdepositing a water solution of a reactive partial condensation productcomposed largely of o-hydroxy benzyl alcohol and o-methylol-p-methylolphenol on and within the fibrous structure of an absorptive fibrousREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,917,815 Schmidt et a1 July 11,1933 1,996,757 Elbel Apr. 9, 1935 2,091,183 Murray et al Aug. 24, 19372,190,672 Meharg Feb. 20, 1940 2,240,480 Dlllehay May 6, 1941 2,360,376Van Epps Oct. 17, 1944

1. A METHOD OF MAKING MOLDING COMPOSITION COMPRISING THE STEPS OFIMPREGNATING AN ABSORBENT FIBROUS FILLER WITH AN IMPREGNANT CONSISTINGESSENTIALLY OF A REACTIVE PARTIAL CONDENSATION PRODUCT COMPOSED LARGELYOF O-HYDROXY BENZYL ALCOHOL AND O-METHYLOL-P-METHYLOL PHENOL HAVING ANAVERAGE MOLECULAR WEIGHT BELOW 300 DISSOLVED IN WATER, AND REMOVING ASUBSTANTIAL PORTION OF THE WATER FROM SAID IMPREGNATED FILLER BY ROLLMILLING.